Leonardo da Vinci (1452-1519) drew a great many things. His notebooks are full of sketches of an amazingly mixed collection of observations and inventions. (To learn more about Leonardo's work and life, have a look at this site from the National Museum of Science and Technology in Milan.)

Inevitably, some of Leonardo's ideas and drawings were about machines that could throw things...

...but first, let's clear up a common error...

This is Not a Leonardo Catapult...Strangely enough, the most commonly quoted example of a "Leonardo" catapult (at least on the internet) isn't one of his drawings at all.
Ralph Payne-Gallway, in his early 20th century book "The Crossbow", included a section on catapults and mis-attributed a drawing by Kolderer as one of Leonardo's.
A quick comparison of drawing style will show that this low-slung heavy trebuchet loaded with a dead horse isn't related to the elegant machines on this page.
While it's certainly possible that this is a crude re-print, the design's impossible proportions are most unlike Leonardo's work.

...now lets look at some machines from Leonardo's sketch books...

Fixed Counter-weight TrebuchetHere Leonardo presents a light fixed-counterweight trebuchet (ie the counterweight is rigidly attached to the beam). The axle pivots at the top of tall posts which are supported and steadied by timbers projecting back from the top of the wall.
The trebuchet's sling appears to simply lie on the ground, although he has drawn something on the ground as well. It may be shadow, or it may be some sort of sliding surface for the sling.

There is a device drawn to the left of the trebuchet that may be an idea for winding the beam down to load the catapult. It shows a toothed wheel with an arm attached and something below it. It's very tempting to see this as a "worm gear" screw winch (a device he uses elsewhere)...
If this is the case it would require two other things: a method of removing the screw from the toothed wheel to allow the trebuchet to shoot - and a method of holding the trebuchet from shooting while this was done. In this little sketch the toothed wheel appears to be prevented from turning by a piece of wood propped up in front of it.

Trebuchet enthusiasts have pointed out that the clever use of the fortification's wall to achieve a high axle means that this design can be given an almost vertical "cocked" position - maximising the height through which the counterweight can fall.
The very high ratio of throwing arm length to counterweight arm length (nearly 8:1) and the light beam construction all point to Leonardo intending this machine as a way of throwing fairly light projectiles.

As this trebuchet was draw sometime around the end of the 15th century, it seems likely that it was intended to fling "grenades" or other gunpowder-filled devices into a besieging force's ranks... although a simple rock travelling at speed (and launched from a considerable height) could do serious damage to an attacker.

"Simple" Spring CatapultThis machine is a fairly simple bent spring device, getting its throwing power by bending back the arm like a single limb of a bow.
There are a number of interesting details in the design. - The arm is fitted with a sling AND a cup so that it throws two projectile simultaneously ... presumably at two considerably different ranges (a sling gives a catapult throw much greater distance).. - The arm has its bottom end resting against a transverse base timber, rather than relying on being set into the ground. - The arm is hauled down by a winch on the diagonal support which acts through a block and tackle that, in turn, is connected to the sling. A trigger, whose lanyard can be seen draped to the rear of the machine, holds the sling. - The rope from halfway up the arm to the base (via a pulley on the diagonal support) may be a mechanism for restraining the arm during a shot, which would give some control over the projectile's launch angle. (This is highly conjectural) - There are what appear to be a series of rungs or pins through the lower end of the arm. This could be a method of setting the diagonal support's angle, or it could be intended for crew access to the arm for reloading when it is standing upwards (although what appears to be a step ladder ahead of the machine seems a more likely means of access).

Complex Spring CatapultIn this design Leonardo takes the idea of the simpler machine shown above and adds to it, with springs acting upon springs.
The throwing arm is boosted by being pushed forwards by a pair of additional arms which are, themselves, boosted by having their back ends pulled up by a trio of additional springs.
Leonardo has used a screw winch in a tray in the base to wind the beam down.
As in the previous machine, the sling is used to connect the arm to the winch.
There is no obvious trigger shown.
The screw winch is shown provided with handles at both ends - allowing more "muscle power to be applied during loading.
Each spring is shown with anchor points for each end and being bent around either a timber pressed against the frame (ie the rear springs) or some form of axle or bolt (ie the front two springs).

Springald on a Swivel MountingThis drawing is of an existing device, the framed torsion weapon called a springald or springarda. The inward-facing "bow" arms can be seen here, as can the torsion bundles that power the device.
This machine is a bolt thower - and the tip of the bolt can be seen projecting forward of the frame at the right. (The drawing further right of this again is a detail of the frame's joinery)
These arms and the bundles are not the usual seen in other torsion machine drawings or reconstructions - Leonardo has shown two modest bundles holding a square structure connected to what looks like four arms in a cross. What this achieves can only be conjured upon - but he may be trying to maximise the twist given to the ropes - which seem to be bowing the frame inwards in this illustration. Why the four arms? One possiblity is that this allows pre-tensioning of the bundles - or some kind of power adjustment to the machine before stringing.

As in many of the other machines, Leonardo has provided this one with a screw winch to draw back the bowstring.

"Bowed" SpringaldHere Leonardo explores the idea of making a new version of an existing torsion-powered device work in a new way - by mounting the twisted rope bundles on bow-like springs.
Re-enactor and replica-builders' experience seems to count against this as a powerful torsion design. In most true torsion machines an almost-completely rigid frame is sought to maximise the power of the twisted rope.
Instead, this machine appears to be an attempt to take the springald concept of the frame-mounted torsion weapon with inward-facing arms, and adapt it to use powerful springs to create the same motion.
In this machine the projectile is a ball (perhaps a gunpowder grenade, perhaps a stone) and rests on a narrow track on the top of the frame.
No mechanism is shown for drawing back the pouch containing the projectile.

Double "Onager"

This machine is shows a similar line of thinking to the "bowed" springald shown above - but here Leonardo takes the concept even further, making the bows more massive, using their tips rather than the middle of each bow, and fitting the system with two throwing arms rather than a "bowstring".
One arm is fitted with a sling - the other, slightly offset, appears to have a rock sitting on a flat rest rather than a sling (possibly to avoid fouling the first arm).
As with the other "two projectile" machine (shown here) the projectiles can be expected to have quite different ranges, with the one in the sling going significantly further.

Leonardo has used the same idea of having the power cords (not quite torsion bundles) passing through discs to which the arms are attached.
Here though he adds teeth to the rims of the discs. It seems plausible that they are engaging a worm gear screw winch below them, allowing the catapult to be "set".
If so, the trigger pin (apparently needing to be struck by a mallet to shoot) may drop the worm drive down, out of contact with the disc peg teeth, and freeing the two arms.

nb note how a similar peg-toothed disc is shown next to the "Fixed Counter-weight trebuchet" drawing, supporting the idea that this is a winch for setting the machine.

Giant Crossbow

Leonardo seems to be taking things a bit far here!
"Great crossbows" had been in use for some time, but these tended to be just moderately oversized heavy crossbows mounted on stands.
This machine is a true giant and looks like a complex engineering solution to a problem that gunpowder artillery had overcome decades earlier.

The details of the bow construction and the trigger mechanism are, however, typically brilliant.
The trigger block moves forward to engage the bowstring and is then wound back on a long screw that passes through it. This screw is, in turn, rotated by a large toothed wheel at the rear end that is turned by a worm-gear which is wound from 6-spoked handles on the side of the machine (just in front of the back wheels).
The design can be triggered by two possible methods - in one the sear holding the "bowstring" is knocked down with a blow from a large hammer, while in the other method it is pivoted in the middle and its opposite end is levered up by a rod passing over a fulcrum.
The giant crossbow in the main drawing seems to be fitted with the latter type of trigger - and the soldier can be seen plying the crowbar to set it off.

That this is intended as a stone (or bomb) thrower is shown by the incorporation of the double bowstring holding a pouch - a feature of small hand-held sporting pellet-shooting crossbows of the time.

n.b. This drawing appears in books in two forms - in this view and in its mirror image. I have chosen to display the view that shows "mirror writing", but this may not be valid.

Great Crossbows

These drawings are a part of the same page as the swivel mounted springald (just visible at the top right).
These aren't really "catapults" any more than a normal crossbow is. The sketches are views of a heavy crossbow (perhaps as much as double normal size) set on tripod mount.
Other, earlier drawings of great crossbows show weapons more like this one. I have included the drawings to provide a contrast with the monster shown above.

Why Draw Designs of Catapults in the Late Fifteenth Century?In a world where gunpowder weapons were already common - even "everyday" - it seems a little odd that Leonardo drew (and promoted) so many mechanical throwing machines. Perhaps it's worth recalling that at this time the longbow and the crossbow were still formidable weapons - and many soldiers fought with ancient tools such as swords or pole weapons like bills, glaives, etc.
Weapons treatises of the late fifteenth and early sixteenth centuries show a mixture of old mechanical artillery and gunpowder weapons.

Leonardo certainly didn't restrict his artillery designing to trebuchets and catapults - he also looked into many aspects of conventional cannon manufacture - and even seems to have designed a steam-powered gun. A line from a "job application" written by Leonardo to Ludovico "the Moor" puts this into context:" Where the use of cannon is impracticable I can replace them with catapults and engines for casting shafts with wonderful and hitherto unknown effect; briefly, whatever the circumstances I can contrive countless methods of attack. ... In the event of a naval battle I have numerous engines of great power both for attack and defense: vessels which are proof against the hottest fire, powder or steam. "

Leonardo drew other hurling machines - and these will be added to the site as illustrations come to hand.